1. Field of the Invention
This invention relates in general to semiconductor devices and in particular to forming semiconductor devices with strained channel regions.
2. Description of the Related Art
Electron and hole motilities may be enhanced with the utilization of strained (e.g. with a bi-axial tensile strain) silicon for the channel region, especially for devices built from wafers having semiconductor or insulator configurations (SOI). A strained silicon layer maybe formed by depositing a layer of silicon on a template layer (e.g. silicon germanium). In some processes, a condensation process is performed on the silicon germanium template to relax the layer prior to the deposition of silicon. One such example of a condensation process includes the oxidization of the silicon germanium template layer. With such a process, a layer of SiO2 is grown on top of the template layer with the germanium of the consumed portion of the template layer diffused into the remaining portion of the silicon germanium layer below to enrich the remaining portion. The oxide is subsequently etched off prior to the deposition of the strained silicon.
One problem that may occur with such a method is that the germanium may not adequately diffuse to the remaining portion of the silicon germanium layer. Accordingly, there may be a relatively high concentration of germanium at the top portion of the remaining layer as opposed to the germanium concentration of the lower portion of the silicon germanium layer. These differences in germanium concentration in the template layer may cause dislocations which could lead to a dysfunctional semiconductor device formed in the area of the dislocations.
What is needed is an improved process for the manufacture of semiconductor devices.
The use of the same reference symbols in different drawings indicates identical items unless otherwise noted. The Figures are not necessarily drawn to scale.